Python Mechanize select form FormNotFoundError

I want to select a form with mechanize. This is my code:

br = mechanize.Browser()
self.br.open(url)
br.select_form(name="login_form")

The form开发者_JS百科's code:

<form id="login_form" onsubmit="return Index.login_submit();" method="post" action="index.php?action=login&server_list=1">

But I'm getting this Error:

mechanize._mechanize.FormNotFoundError: no form matching name 'login_form

The problem is that your form does not have a name, only an id, and it is login_form. You can use a predicate:

br.select_form(predicate=lambda f: f.attrs.get('id', None) == 'login_form')

(where you se if f.attrs has the key id and, if so, the id value is equal to login_form). Alternatively, you can pass the number of the form in the page, if you know if it is the first one, the second one etc. For example, the line below selects the first form:

br.select_form(nr=0)

a little more readable:

class Element_by_id:
    def __init__(self, id_text):
        self.id_text = id_text
    def __call__(self, f, *args, **kwargs):
        return 'id' in f.attrs and f.attrs['id'] ==self.id_text

then:

b.select_form(predicate=Element_by_id("login_form"))